Snowdrop genes provide key to fight pest attack

By Edward Long

GENES extracted from snowdrops and cow peas have been inserted into oilseed rape, potatoes, lettuce, and tomato plants to provide in-built protection from nematodes, aphids and other sucking insect pests.

That will bolster the plants natural defences against invading pests, so reducing the need for pesticides.

Early indications from trials with genetically-transformed rape at Rothamsted Experimental Station suggest worthwhile nematode control is possible. Researchers now plan to "beef-up" its effectiveness.

"By the turn of the century mainstream arable crops, and some high value horticultural crops, with the genetic in-built protection against these highly damaging pests will be in field trials," predicts Dr Iain Cubitt, managing director of Cambs-based Axis Genetics of Babraham. The company has global rights to the snowdrop gene GNA.

Ready in 10 years

"If these trials are successful, crop varieties incorporating the GNA gene should be commercially available within 10 years."

The story started when Belgian researchers at Leuven University found a protein in snowdrop which interferes with natural reproduction and larval development of a range of plant pests.

British collaboration between Axis Genetics and the University of Durham subsequently identified the gene responsible for producing that protein.

No one yet knows how it works. It does not kill pests – indeed some continue to feed. But their ability to breed is disrupted and populations fail to reach threatening levels.

Aphids are particularly badly affected. That reduces, or possibly even eliminates, the need for knock-down chemical treatments.

The new gene could be expressed in plant roots or leaves to give specific protection. Unlike most other plant-produced lectins, the snowdrop protein is not toxic to mammals.

At the International Potato Center in Peru, GNA is being inserted into the tuber crop to provide novel resistance against both nematodes and aphids. In the USA researchers are working on wheat, Cornell University in New York is putting it into rice, and it is being transferred into sugar cane by Australian scientists.

In this country oilseed rape and potato growers are likely to benefit first – the gene has already been successfully transferred.

Transgenic potatoes were multiplied at Rothamsted this year for a trial in 1996 to assess the merits of the approach.

Modified rape plants were tested against both free-living and cyst nematodes in glasshouse trials this year. "We introduced them and allowed them to feed, and by counting them in at the start of the trial, and out at the end we were able to assess the level of control," explains Rothamsteds Dr Paul Burrows.

Dramatic combination

"The snowdrop gene used alone had a slight effect. But when it was used in combination with a gene extracted from cow peas the result was dramatic. It was a case of one plus one equalling more than two, in fact it was 10+."

The cow pea gene is a tripsin inhibitor and upsets protein digestion in the pests gut. The combination of the two genes was particularly effective against free-living nematodes, a 70% reduction in numbers was recorded. There was less effect against cysts, numbers were reduced by about 30%.

"This was an exciting first-year result. For 1996 we hope to be able to beef-up the level of control and develop cocktails of genes to provide plants with an even more effective in-built defence system," Dr Burrows says. &#42